Originality or Plagiarism

I feel as though true originality is one of the most difficult things to create, because every idea comes from another. This is evident everywhere in life. However, creative genius is still a product of plagiarism. I think that is maybe one of the most important aspect of new things, able to create them from another. So while I don't know if all work is plagiarized, I think that most creative genius is influenced immensely by the work of others.